Fronthaul interface for a centralized radio access network

ABSTRACT

One embodiment is directed to a system that is configured to communicate at least two different types of fronthaul data from a plurality of baseband units to a shared radio point using a single application-layer protocol that supports at least two types of elements. Each of the at least two types of elements is configured for a respective one of the at least two different types of fronthaul data. The system is configured so at least some of the elements communicated using the application-layer protocol include one or more sub-elements, where each sub-element comprises a type field, a length field, and a value portion.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.15/931,367, filed on May 13, 2020, which claims the benefit of U.S.Provisional Patent Application Ser. No. 62/847,794, filed on May 14,2019, all of which are hereby incorporated herein by reference in theirentirety.

BACKGROUND

A centralized radio access network (C-RAN) can be used to implement basestation functionality for providing wireless service to various items ofuser equipment (UE). Typically, for each cell implemented by the C-RAN,one or more baseband units (BBUs) (also referred to here as “basebandcontrollers” or simply “controllers”) interact with multiple remoteunits (also referred to here as “radio points” or “RPs”).

In one common configuration, a controller is coupled to each radio pointit serves over one or more synchronous point-to-point communicationlinks. For example, each controller can be coupled to each radio pointit serves over a pair of synchronous optical links that implement CommonPublic Radio Interface (CPRI) specification, one of which is used forcommunicating downlink front-haul data and the other of which is usedfor communicating uplink front-haul data.

In such a configuration, the controller performed all of the digitalLayer-1, Layer-2, and Layer-3 processing for the air interface, whilethe radio points implement only the analog RF transceiver functions forthe air interface. As a result, the downlink and uplink front-haul datathat is communicated between the controller and each radio point overthe CPRI links comprises in-phase and quadrature (IQ) data representingtime-domain symbols for the air interface.

Deploying such special-purpose CPRI synchronous optical links, however,is typically more expensive and less convenient than using switchedEthernet networks to implement the fronthaul in a C-RAN.

SUMMARY

One embodiment is directed to a system to provide wireless service. Thesystem comprises at least one controller and a plurality of radiopoints. Each of the radio points is associated with at least one antennaand remotely located from the controller. The plurality of radio pointsis communicatively coupled to the controller. The controller and theplurality of radio points are configured to implement at least one basestation in order to provide wireless service via a wireless interface toa plurality of user equipment (UEs) using at least one cell. Thecontroller is communicatively coupled to a core network of a wirelessservice provider. The system is configured so that physical layerprocessing for the wireless interface is split so that some of thephysical layer processing is performed in the controller and some of thephysical layer processing is performed in the radio points. The systemis configured so that scrambling of first downlink data to becommunicated to a UE over the wireless interface is performed in thecontroller and so that scrambling of second downlink data to becommunicated to said UE over the wireless interface is performed in atleast one of the radio points.

Another embodiment is directed to a system to provide wireless service.The system comprises at least one controller and a plurality of radiopoints. Each of the radio points is associated with at least one antennaand remotely located from the controller. The plurality of radio pointsis communicatively coupled to the controller. The controller and theplurality of radio points are configured to implement at least one basestation in order to provide wireless service via a Long-Term Evolution(LTE) wireless interface to a plurality of user equipment (UEs) using atleast one cell. The controller is communicatively coupled to a corenetwork of a wireless service provider. The system is configured so thatphysical layer processing for the wireless interface is split so thatsome of the physical layer processing is performed in the controller andsome of the physical layer processing is performed in the radio points.The system is configured so that signal generation and modulation forPrimary Synchronization Signals (PSS) and Secondary SynchronizationSignals (SSS) are performed entirely in the radio points and signalgeneration and modulation for Cell-Specific Reference Signals (CS-RSs)and Channel State Information Reference Signals (CSI-RSs) are performedentirely in the radio points. The system is configured so that, for aPhysical Downlink Control Channel (PDCCH), downlink Layer-1 signalprocessing for the LTE wireless interface up to, and including, ascrambling function is performed in the controller. A portion of aresource element (RE) mapping function for the PDCCH is also performedin the controller. The downlink Layer-1 signal processing for the PDCCHnot performed in the controller is performed in the radio points. Thesystem is configured so that, for a Physical Downlink Shared Channel(PDSCH), downlink Layer-1 signal processing for the LTE wirelessinterface up to, and including, a scrambling function for data to betransmitted and generation of associated demodulation reference signals(DMRSs) are performed in the controller. The downlink Layer-1 signalprocessing for the PDSCH not performed in the controller is performed inthe radio points.

Another embodiment is directed to a system to provide wireless service.The system comprises at least one controller and a plurality of radiopoints. Each of the radio points is associated with at least one antennaand remotely located from the controller. The plurality of radio pointsis communicatively coupled to the controller. The controller and theplurality of radio points are configured to implement at least one basestation in order to provide wireless service via a Fifth Generation NewRadio (5G-NR) wireless interface to a plurality of user equipment (UEs)using at least one cell. The controller is communicatively coupled to acore network of a wireless service provider. The system is configured sothat physical layer processing for the wireless interface is split sothat some of the physical layer processing is performed in thecontroller and some of the physical layer processing is performed in theradio points. The system is configured so that signal generation andmodulation for Primary Synchronization Signals (PSS) and SecondarySynchronization Signals (SSS) are performed entirely in the radiopoints. The system is configured so that signal generation andmodulation for Phase Tracking Reference Signals (PTRSs) and ChannelState Information Reference Signals (CSI-RSs) are performed entirely inthe radio points. The system is configured so that, for a PhysicalDownlink Control Channel (PDCCH), downlink Layer-1 signal processing forthe 5G-NR wireless interface up to, and including, a scrambling functionfor data to be transmitted and generation of associated demodulationreference signals (DMRSs) are performed in the controller. A portion ofa resource element (RE) mapping function for the PDCCH is also performedin the controller. The downlink Layer-1 signal processing for the PDCCHnot performed in the controller is performed in the radio points. Thesystem is configured so that, for a Physical Downlink Shared Channel(PDSCH), downlink Layer-1 signal processing for the 5G-NR wirelessinterface up to, and including, a scrambling function for data to betransmitted and generation of associated DMRSs are performed in thecontroller. The downlink Layer-1 signal processing for the PDSCH notperformed in the controller is performed in the radio points.

Other embodiments are disclosed.

The details of various embodiments are set forth in the accompanyingdrawings and the description below. Other features and advantages willbecome apparent from the description, the drawings, and the claims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A is a block diagram illustrating one exemplary embodiment of aradio access network (RAN) system in which the multi-carrier radiopoints described here can be used.

FIG. 1B is a block diagram illustrating one exemplary embodiment of asingle-instance radio point unit that can be used to implement a singleinstance of a radio point of the C-RAN of FIG. 1A.

FIG. 1C is a block diagram illustrating one exemplary embodiment of amultiple-instance radio point unit that can be used to implement one ormore instances of a radio point for one or more C-RANs of the type shownin FIG. 1A.

FIG. 2 illustrates additional details about implementing the fronthaulfor the C-RAN using a switched Ethernet network.

FIG. 3 illustrates one example of how the IP and application-layermulticast groups can be used to communicate downlink IQ data over theswitched Ethernet network from the serving controller to the radiopoints.

FIG. 4 is a diagram illustrating one exemplary embodiment of a protocolstack suitable for communicating IQ data between each controller and theassociated radio points over the front-haul.

FIG. 5 illustrates one example of a Type-Length-Value (TLV) element.

FIG. 6 illustrates one example of the different splits in thewireless-interface processing between the controller and the radiopoints that can be used for the various downlink channels provided viaan LTE wireless interface.

FIG. 7 illustrates one example of the different splits in thewireless-interface processing between the controller and the radiopoints that can be used for the downlink channels of a Fifth Generation(5G)-New Radio (NR) wireless interface.

FIG. 8 illustrates another example of a split in the wireless-interfaceprocessing between the controller and the radio points that can be usedwith the PDSCH.

FIG. 9 illustrates one exemplary embodiment of a TLV element forcommunicating downlink IQ data over the fronthaul in a C-RAN.

FIG. 10 illustrates one exemplary embodiment of aPDSCH-CONFIG-and-FEC-BITS sub-TLV element.

FIG. 11 illustrates one exemplary embodiment of aPDSCH-PADDING-and-FEC-BITS sub-TLV element.

Like reference numbers and designations in the various drawings indicatelike elements.

DETAILED DESCRIPTION

FIG. 1A is a block diagram illustrating one exemplary embodiment of aradio access network (RAN) system 100 in which the multi-carrier radiopoints described here can be used. The system 100 is deployed at a site102 to provide wireless coverage and capacity for one or more wirelessnetwork operators. The site 102 may be, for example, a building orcampus or other grouping of buildings (used, for example, by one or morebusinesses, governments, or other enterprise entities) or some otherpublic venue (such as a hotel, resort, amusement park, hospital,shopping center, airport, university campus, arena, or an outdoor areasuch as a ski area, stadium or a densely-populated downtown area).

In the exemplary embodiment shown in FIG. 1A, the system 100 isimplemented at least in part using a C-RAN architecture that employsmultiple baseband units 104 and multiple radio points (RPs) 106. Thesystem 100 is also referred to here as a “C-RAN system” 100. Each RP 106is remotely located from the baseband units 104. Also, in this exemplaryembodiment, at least one of the RPs 106 is remotely located from atleast one other RP 106. The baseband units 104 and RPs 106 serve atleast one cell 108. The baseband units 104 are also referred to here as“baseband controllers” 104 or just “controllers” 104.

Each RP 106 includes or is coupled to one or more antennas 110 via whichdownlink RF signals are radiated to various items of user equipment (UE)112 and via which uplink RF signals transmitted by UEs 112 are received.

Each controller 104 and RP 106 (and the functionality described as beingincluded therein), as well as the system 100 more generally, and any ofthe specific features described here as being implemented by any of theforegoing, can be implemented in hardware, software, or combinations ofhardware and software, and the various implementations (whetherhardware, software, or combinations of hardware and software) can alsobe referred to generally as “circuitry” or a “circuit” configured toimplement at least some of the associated functionality. Whenimplemented in software, such software can be implemented in software orfirmware executing on one or more suitable programmable processors. Suchhardware or software (or portions thereof) can be implemented in otherways (for example, in a field programmable gate array (FPGA),application specific integrated circuit (ASIC), etc.). Also, the RFfunctionality can be implemented using one or more RF integratedcircuits (RFICs) and/or discrete components. Each controller 104 and RP106, and the system 100 more generally, can be implemented in otherways.

The system 100 is coupled to the core network 114 of each wirelessnetwork operator over an appropriate back-haul. In the exemplaryembodiment shown in FIG. 1A, the Internet 116 is used for back-haulbetween the system 100 and each core network 114. However, it is to beunderstood that the back-haul can be implemented in other ways.

The exemplary embodiment of the system 100 shown in FIG. 1A is describedhere as being implemented as a Long Term Evolution (LTE) radio accessnetwork providing wireless service using an LTE air interface. LTE is astandard developed by 3GPP standards organization. In this embodiment,the controllers 104 and RPs 106 together are used to implement one ormore LTE Evolved Node Bs (also referred to here as an “eNodeBs” or“eNBs”) that are used to provide user equipment 112 with mobile accessto the wireless network operator's core network 114 to enable the userequipment 112 to wirelessly communicate data and voice (using, forexample, Voice over LTE (VoLTE) technology). These eNodeBs can be macroeNodeBs or home eNodeBs (HeNB).

Also, in this exemplary LTE embodiment, each core network 114 isimplemented as an Evolved Packet Core (EPC) 114 comprising standard LTEEPC network elements such as, for example, a mobility management entity(MME) and a Serving Gateway (SGW) (all of which are not shown). Eachcontroller 104 communicates with the MME and SGW in the EPC core network114 using the LTE S1 interface. Also, each controller 104 communicateswith other eNodeBs using the LTE X2 interface. For example, eachcontroller 104 can communicate via the LTE X2 interface with an outdoormacro eNodeB (not shown) or another controller 104 in the same cluster124 (described below) implementing a different cell 108.

If the eNodeB implemented using one or more controllers 104 is a homeeNodeB, the core network 114 can also include a Home eNodeB Gateway (notshown) for aggregating traffic from multiple home eNodeBs.

The controllers 104 and the radio points 106 can be implemented so as touse an air interface that supports one or more of frequency-divisionduplexing (FDD) and/or time-division duplexing (TDD). Also, thecontrollers 104 and the radio points 106 can be implemented to use anair interface that supports one or more of themultiple-input-multiple-output (M IMO), single-input-single-output(SISO), single-input-multiple-output (SIMO), and/or beam formingschemes. For example, the controllers 104 and the radio points 106 canimplement one or more of the LTE transmission modes using licensedand/or unlicensed RF bands or spectrum. Moreover, the controllers 104and/or the radio points 106 can be configured to support multiple airinterfaces and/or to support multiple wireless operators.

The controllers 104 are communicatively coupled to the radio points 106using a front-haul network 118. In the exemplary embodiment shown inFIG. 1A, the front-haul 118 that communicatively couples each controller104 to one or more RPs 106 is implemented using a standard switchedEthernet network 120. However, it is to be understood that thefront-haul between the controllers 104 and RPs 106 can be implemented inother ways (for example, the front-haul between the controllers 104 andRPs 106 can be implemented using private networks and/or public networkssuch as the Internet).

In the exemplary embodiment shown in FIG. 1A, a management system 122 iscommunicatively coupled to the controllers 104 and RPs 106, for example,via the Internet 116 and Ethernet network 120 (in the case of the RPs106).

In the exemplary embodiment shown in FIG. 1 , the management system 122communicates with the various elements of the system 100 using theInternet 116 and the Ethernet network 120. Also, in someimplementations, the management system 122 sends and receives managementcommunications to and from the controllers 104, each of which in turnforwards relevant management communications to and from the RPs 106. Themanagement system 122 can comprise a proprietary management systemprovided by the vendor of the C-RAN system 100 or a Home eNodeBmanagement system (HeNB MS) (or other eNodeB management system) used byan operator to manage Home eNodeBs (or other eNodeBs) deployed in itsnetwork.

Each controller 104 can also implement a management interface by which auser is able to directly interact with the controller 104. Thismanagement interface can be implemented in various ways including, forexample, by implementing a web server that serves web pages thatimplement a web-based graphical user interface for a user to interactwith the controller 104 using a web browser and/or by implementing acommand-line interface by which a user is able to interact with thecontroller 104, for example, using secure shell (SSH) software.

In the exemplary embodiment shown in FIG. 1A, the system 100 comprisesmultiple controllers 104 that are grouped together into a cluster 124.Each cluster 124 is used to serve a set of cells 108, where each cell108 has an associated set of RPs 106 that have been assigned to thatcell 108 and that are served by one or more of the controllers 104included in that cluster 124. The association of radio points 106 withcells 108 is implemented using a “white list” that associates a radiopoint identifier (for example, a media access control (MAC) address)with an identifier associated with an associated cell 108 (for example,a logical or virtual cell identifier used within the context of theC-RAN 100).

In the example described here in connection with FIG. 1A, each radiopoint 106 can be implemented using a single-instance radio point unit180 as shown in FIG. 1B or as a multiple-instance radio point unit 190as shown in FIG. 1C.

FIG. 1B is a block diagram illustrating one exemplary embodiment of asingle-instance radio point unit 180 that can be used to implement asingle instance of a radio point 106 of the C-RAN 100 of FIG. 1A.

In this exemplary embodiment, the single-instance radio point unit 180comprises a single radio frequency (RF) module 182. The RF module 182comprises circuitry that implements the RF transceiver functions for asingle instance of a radio point 106 and provides an interface to one ormore antennas 110 associated with that instance of the radio point 106.More specifically, in the exemplary embodiment shown in FIG. 1B, each RFmodule interfaces 182 with a respective two antennas 110.

Each RF module 182 comprise circuitry that implements, for theassociated instance of a radio point 106, two downlink signal paths, onefor each of the two antennas 110, and two uplink signals paths, one foreach of the two antennas 110. In one exemplary implementation, eachdownlink signal path comprises a respective digital-to-analog converter(DAC) to convert downlink digital samples to a downlink analog signal, arespective frequency converter to upconvert the downlink analog to adownlink analog RF signal at the desired RF frequency, and a respectivepower amplifier (PA) to amplify the downlink analog RF signal to thedesired output power for output via the antenna 110 associated with thatdownlink signal path. In one exemplary implementation, each uplinksignal path comprises a respective low-noise amplifier (LNA) foramplifying an uplink analog RF signal received via the antenna 110associated with the uplink signal path, a respective frequency converterto down-convert the received uplink analog RF signal to an uplink analogbaseband frequency signal, a respective analog-to-digital converter(ADC) to convert the uplink analog baseband frequency signal to uplinkdigital samples. Each of the downlink and uplink signal paths can alsoinclude other conventional elements such as filters. Each RF module canbe implemented using one or more RF integrated circuits (RFICs) and/ordiscrete components.

The single-instance radio point unit 180 further comprises at least onenetwork interface 184 that is configured to communicatively couple thesingle-instance radio point unit 180 to the front-haul network 118. Morespecifically, in the exemplary embodiment shown in FIG. 1B, the networkinterface comprises an Ethernet network interface that is configured tocommunicatively couple that single-instance radio point unit 180 to theswitched Ethernet network 120 that is used to implement the front-haul118 for the C-RAN 100.

The single-instance radio point unit 180 further comprises one or moreprogrammable devices 186 that execute, or are otherwise programmed orconfigured by, software, firmware, or configuration logic in order toimplement Layer-1 (physical layer) baseband processing described here asbeing performed by the instance of a radio point 106 implemented usingthat single-instance radio point unit 180. The one or more programmabledevices 186 can be implemented in various ways (for example, usingprogrammable processors (such as microprocessors, co-processors, andprocessor cores integrated into other programmable devices),programmable logic (such as field programmable gate arrays (FPGA), andsystem-on-chip packages)). Where multiple programmable devices are used,all of the programmable devices do not need to be implemented in thesame way. In the exemplary embodiment shown in FIG. 1B, memory 188included in the radio point unit 180 is used by the programmable devices186. Memory 188 can comprise memory that is integrated into and/or thatis external to the programmable devices 186 (as illustrated in FIG. 1B).

FIG. 10 is a block diagram illustrating one exemplary embodiment of amultiple-instance radio point unit 190 that can be used to implement oneor more instances of a radio point 106 for one or more C-RANs 100 of thetype shown in FIG. 1A.

In this exemplary embodiment, the multiple-instance radio point unit 190comprises multiple RF modules 182. In general, each RF module 182 isimplemented as described above in connection with FIG. 1B, except thatthe multiple radio point unit 190 includes multiple RF modules 182instead of a single RF module 182. In one implementation of theembodiment shown in FIG. 10 , one RF module 182 is used for eachinstance of a radio point 106 that is implemented using themultiple-instance radio point unit 190.

The multiple-instance radio point unit 190 further comprises at leastone network interface 184 that is configured to communicatively couplethe multiple-instance radio point unit 190 to the fronthaul network 118of each C-RAN 100 with which the unit 190 is being used. In general,each RF module 182 is implemented as described above in connection withFIG. 1B.

The multiple-instance radio point unit 190 further comprises one or moreprogrammable devices 186 and memory 188. In general, the one or moreprogrammable devices 186 and memory 188 included in themultiple-instance radio point unit 190 are implemented as describedabove in connection with FIG. 1B, except that the programmable devices186 and memory 188 are scaled so as to be able implement multipleinstances of a radio point 106 instead of only a single instance of aradio point 106, as is the case with the single-instance radio pointunit 180 of FIG. 1B.

In the exemplary embodiment shown in FIG. 10 , each of the multipleinstances of a radio point 106 implemented using the multiple-instanceradio point unit 190 can be implemented using a separate “slice” 187 ofthe programmable devices 186 that are dedicated to implementing thatradio point instance. However, in order to support efficientimplementation of, and communications between, radio points instancesimplemented on the same multiple-instance radio point unit 190, themultiple-instance radio point unit 190 can be configured so that atleast some of the resources of the multiple-instance radio point unit190 (for example, resources provided by the programmable devices 186 ormemory 188) are shared among the slices 187 used to implement thevarious radio instances. In one example, the various radio pointinstances implemented by a single multiple-instance radio point unit 190use shared memory 188 to communicate with each other using internalmessaging (via the shared memory 188), thereby avoiding the need forsuch communications to occur over the fronthaul network 118.

The multiple-instance radio point unit 190 is configured to implementmultiple instances of a radio point 106, where each such radio pointinstance appears to the associated serving controller 104 as a separatelogical radio point 106. Each instance of a radio point 106 isimplemented using one or more RF modules 182 and one or more slices 187of the programmable devices 186. For example, in the embodiment shown inFIG. 10 , a 2×2 MIMO instance of a radio point 106 can be implementedusing a single RF module 182 and a single slice 187 of the programmabledevices 186, whereas a 4×4 MIMO instance of a radio point 106 can beimplemented using two RF modules 182 and two slices 187 of theprogrammable devices 186. Other examples and embodiments can beimplemented in other ways.

Generally, for each cell 108 implemented by the C-RAN 100, thecorresponding controller 104 performs the Layer-3 and Layer-2 processingfor the wireless interface as well as at least some of the Layer-1(physical layer) processing for the wireless interface, where each ofthe radio points 106 serving that cell 108 performs the Layer-1processing not performed by the controller 104 as well as implementingthe analog RF transceiver functions.

Different splits in the wireless-interface processing between thecontroller 104 and the radio points 106 can be used for each of thephysical channels of the wireless interface. That is, the split in thewireless-interface processing between each controller 104 and the radiopoints 106 used for one or more downlink physical channels of thewireless interface can differ from the split used for one or more uplinkphysical channels of the wireless interface. Also, for a given direction(downlink or uplink), the same split in the wireless-interfaceprocessing does not need to be used for all physical channels of thewireless interface associated with that direction.

Appropriate fronthaul data is communicated between the controller 104and the associated radio points 106 over the front-haul 118 in order tosupport each split that is used. In the following description, thefronthaul data communicated between the controllers 104 and the radiopoints 106 for the air interface is generally referred to here as “IQdata” even though such fronthaul data can take many forms, includingforms that are not IQ data.

FIG. 2 illustrates additional details about implementing the fronthaul118 for the C-RAN 100 using a switched Ethernet network 120. In general,the switched Ethernet network 120 comprises one or more Ethernetswitches. In the example shown in FIG. 2 , the switched Ethernet network120 comprises an aggregation layer including one or more aggregationEthernet switches 126 and an access layer including one or more accessEthernet switches 128. Although only one aggregation switch 126 andaccess Ethernet switch 128 is shown in FIG. 2 for ease of illustration,other numbers of switches 126 and 128 can be used. Also, other Ethernetnetwork topologies can be used (for example, there may be additionallayers (or hops) of Ethernet switches between (or within one or more of)the aggregation layer and the access layer or entirely differenttopologies can be used).

As illustrated in more detail in FIG. 2 , in this exemplary embodiment,the controllers 104 and radio points 106 communicate with each otherover the switched Ethernet network 120 used to implement the fronthaul118 using two common virtual local area networks (VLANs). In thisembodiment, one VLAN is used for communicating timing information (forexample, Institute of Electrical and Electronics Engineers (IEEE) 1588Precision Time Protocol (PTP) messages used for synchronizing thecontrollers 104 and RPs 106) and management information (for example,Simple Object Access Protocol (SOAP) and eXtensible Markup Language(XML) messages) between the controllers 104 and the radio points 106.This VLAN is referred to here as the “timing and management” or “TM”VLAN. A second VLAN is used for communicating IQ data between thecontrollers 104 and the radio points 106 and is referred to here as the“IQ” VLAN.

In this embodiment, the TM and IQ VLANs are configured so that all ofthe controllers 104 in a cluster 124 and the associated RPs 106 aremembers of the TM and IQ VLANs.

In the example shown in FIG. 2 , the fronthaul 118 is used forfronthauling data for two clusters 124 serving two respective wirelessoperators. In this example, a separate VLAN is established for eachcluster 124 for inter-controller communications between the controllers104 included that cluster 124. Each such VLAN is referred here as a“cluster” or “C” VLAN.

In the example shown in FIG. 2 , each controller 104 includes multipleEthernet network interfaces 130 for coupling that controller 104 to theswitched Ethernet network 120 (more specifically, to one or moreaggregation switches 126 in the example shown in FIG. 2 ).

In the example shown in FIG. 2 , some of the Ethernet network interfaces130 in each controller 104 are dedicated for communicating timing andmanagement data over the timing and management VLAN. Each such Ethernetnetwork interface 130 is also referred to here as a “timing andmanagement” or “TM” Ethernet network interface 130. In this example,some of the Ethernet network interfaces 130 in each controller 104 arededicated for communicating IQ data over the IQ VLAN and are alsoreferred to here as “IQ” Ethernet network interfaces 130. Also, in thisexample, some of the Ethernet network interfaces 130 in each controller104 are dedicated for communicating over the cluster VLAN. Each suchEthernet network interface 130 is referred to here as a “cluster” or “C”Ethernet network interface 130. Each controller 104 also includes one ormore other Ethernet network interfaces (not shown) that are used forcommunicating over the backhaul with the core network 114.

In the example shown in FIG. 2 , each single-instance radio point unit180 comprises one Ethernet network interface 184 and eachmultiple-instance radio point 190 comprises two Ethernet networkinterfaces 184, where each such Ethernet network interface 184 is usedfor communicating over both the timing and management VLAN and the IQVLAN.

In this embodiment, for each cell 108 served by a cluster 124, thecontroller 104 serving that cell 108 transmits timing messages over thetiming VLAN by multicasting the timing messages using a respectivetiming multicast group defined for that cell 108. That is, each cell 108served by the cluster 124 has a single timing multicast group assignedto it. In this embodiment, for each cell 108 served by a cluster 124,the RPs 106 transmit timing messages over the timing and management VLANby unicasting the messages to the IP address assigned to the Timing andManagement Ethernet interface of the serving controller 104 for thatcell 108.

Also, in this embodiment, for each cell 108 served by a cluster 124,management messages are transmitted between the controllers 104 and theRPs 106 over the timing and management VLAN by unicasting the messagesusing the IP address assigned to the Timing and Management Ethernetinterface of the controller 104 or to an Ethernet interface 184 of theRP 106 to which the message is sent.

A set of downlink and uplink IP multicast groups are used fortransmitting downlink and uplink IQ data, respectively.

The timing, management, and IQ data can be communicated in other ways.

In general, when each radio point 106 boots up, each radio pointinstance implemented by that radio point 106 will use a discoveryprotocol in order to discover the controller 104 that radio pointinstance should be homed to. As a part of the discovery process, theradio point instance will be provided with the IP address assigned tothe Timing and Management Ethernet interface 130 of the discoveredcontroller 104. The radio point instance uses that IP address toestablish a SOAP (management) connection with the controller 104. Thecontroller 104 communicates the IP addresses of the downlink and uplinkIP multicast groups that the radio point instance should use forcommunicating downlink and uplink IQ data.

In configurations where multiple controllers 104 serve a given radiopoint instance (for example, where a controller 104 serves as backupcontroller for another primary controller 104 or where carrieraggregation is used and multiple controllers 104 are used to perform thebaseband processing for the multiple carriers), each radio pointinstance serving a given cell 108 still registers to the appropriatedownlink IP multicast groups for the cell 108 and sends data to thecontrollers 104 over the front-haul 118 using the appropriate uplink IPmulticast groups. Because IP multicast is used, multiple controllers 104can register to, and receive data using, the same uplink IP multicastgroups that the radio point instances for that cell 108 use to send dataover the front-haul 118 and multiple controllers 104 can send data overthe front-haul 118 to the radio point instances for that cell 108 usingthe downlink IP multicast groups that those radio point instancesregister to. That is, the radio point instances can be transparentlyserved by multiple controllers 104 because of the use of IP multicast.

Moreover, the use of IP multicast does not preclude a single controller104 serving multiple cells 108. In configurations where a singlecontroller 104 serves multiple cells 108 (for example, a primary cell108 and a secondary cell 108), that single controller 104 registers tothe uplink IP multicast groups for the primary cell 108 and secondarycell 108 and sends data to the appropriate radio point instances overthe front-haul 118 using the downlink IP multicast cast groups for theprimary cell 108 and secondary cell 108.

In this exemplary embodiment, downlink and uplink IQ data is transmittedbetween each controller 104 and the associated radio points 106 on aUE-by-UE basis. For each UE 112 that is served by the cell 108, theserving controller 104 assigns a subset of that cell's RPs 106 to thatUE 112 for downlink wireless transmissions to that UE 112. This subsetof RPs 106 is referred to here as the “simulcast zone” for that UE 112.The simulcast zone for each UE 112 is determined based on receive powermeasurements made at each of the RPs 106 for certain uplinktransmissions from the UE 112 (for example, LTE Physical Random AccessChannel (PRACH) and Sounding Reference Signals (SRS) transmissions) andis updated as the UE 112 moves throughout the cell 108.

For the uplink, in this embodiment, for each cell 108, the radio points106 serving that cell 108 transmit uplink IQ data to the servingcontroller 104 using a set of uplink IP multicast groups and multicastload balancing. In this embodiment, multiple link aggregation groups(LAGs) are defined for each cell 108, with each LAG having an uplink IPmulticast group associated with it. The switches 126 and 128 in theswitched Ethernet network 120 are configured to use multicast loadbalancing to load balance the uplink IQ data traffic across the variousIQ Ethernet interfaces of the serving controller 104.

As with the uplink, multiple downlink IP multicast groups are used forload balancing purposes. For the downlink, multiple sets of downlink IPmulticast groups are used for sending downlink IQ data to differentcombinations of RPs 106, where the sets of downlink IP multicast groupsare dynamic. For one set of downlink IP multicast groups, each of thedownlink IP multicast groups of that set include all of the RPs 106serving the cell 108. These “all RP” downlink IP multicast groups areused in order to transmit downlink IQ data for common logical channelsof the wireless interface to all of the RPs 106 of the cell 108. Oneexample of where this may be done is for transmitting downlink IQ datafor LTE System Information Blocks (SIBs). An “all RP” downlink IPmulticast group can also be used in the event that there is no othersuitable set of downlink IP multicast groups. For the other sets ofdownlink IP multicast groups, all of the constituent downlink IPmulticast groups contain less than all of the RPs 106 serving the cell108. These other sets of downlink IP multicast groups are created asneeded in order to communicate downlink IQ data (in particular, downlinkIQ data for the Physical Downlink Shared Channel (PDSCH)) to only thoseRPs 106 that are in the simulcast zone for a given UE 112.

When downlink data needs to be transmitted to a given UE 112 over thewireless interface, if there is an existing set of downlink IP multicastgroups that “matches” the simulcast zone for that UE 112, then one ofthe downlink IP multicast groups from the matching set is used fortransmitting downlink IQ data for that UE 112 to the RPs 106 in thatUE's simulcast zone. If there is no set of downlink IP multicast groupsthat matches the simulcast zone of a given UE 112, a new set of downlinkIP multicast groups can be created, where all of the downlink IPmulticast groups of that set include the RPs 106 in that simulcast zoneand then one of those newly created downlink IP multicast groups is usedfor transmitting downlink IQ data to only those RPs 106 in thatsimulcast zone. If it is not possible to create a new matching set ofdownlink IP multicast groups (for example, because the maximum number ofdownlink IP multicast groups has already been created and none of theexisting downlink IP multicast group sets can be purged at that time dueto non-use), then one of the previously mentioned “all RP” downlink IPmulticast groups can be used.

However, using an “all RP” downlink IP multicast group may result indownlink IQ data for a given UE 112 being sent to RPs 106 that are notincluded in that UE's simulcast zone. To deal with this, anapplication-layer multicast address included in the IQ data (asdescribed below) is used in this example to identify which RPs 106 theassociated downlink IQ data is actually intended for. In this example,this application-layer multicast address comprises an address field thatcan be viewed as a plurality of bit positions. A respective one of thebit positions is assigned to each RP 106 serving the cell 108, wherethat bit position is set (that is, stores a first binary value (forexample, one)) if the associated downlink IQ data is intended for theassociated RP 106 and where that bit positioned is cleared (that is,stores a second binary value (for example, zero)) if the associateddownlink IQ data is not intended for the associated RP 106. For example,all of the bit positions of the application-layer multicast addresswould be set for packets including downlink IQ data for common messages(such as SIBs), which are intended for all RPs 106. For downlink IQ dataintended for a UE 112 that includes less than all of the RPs 106 in itssimulcast zone, only the bit positions of the application-layermulticast address that correspond to RPs 106 in that simulcast zone areset, with the bit positions that correspond to all other RPs 106 beingcleared. (One example of an application-layer multicast address is theapplication-layer multicast address field 526 described below inconnection with FIG. 5 .)

FIG. 3 illustrates one example of how the IP and application-layermulticast groups can be used to communicate downlink IQ data over theswitched Ethernet network 120 from the serving controller 104 to theradio points 106. In the example shown in FIG. 3 , five RPs 106 andthree UEs 112 are shown. The RPs 106 are individually referenced in FIG.3 as RP 1, RP 2, RP 3, RP 4, and RP 5, respectively. The UEs 112 areindividually referenced in FIG. 3 as UE A, UE B, UE C, respectively. Inthe example, shown in FIG. 3 , the simulcast zone for UE A includes RP1, RP 2, and RP 4, the simulcast zone for UE B includes RP 4 RP 5, andUE C includes RP 2, RP 3, and RP 5. If UE A, UE B, and UE C all remainin the same location and continue to access the cell 108, three downlinkIP multicast groups will be formed (if they do not already exist). Thesethree downlink IP multicast groups include a first downlink IP multicastgroup including RP 1, RP 2, and RP 4 (and, in this example, is assignedan IP address of 239.2.1.10), a second downlink IP multicast groupincluding RP 4 and RP 5 (and, in this example, is assigned an IP addressof 239.2.1.11), and a third downlink IP multicast group including RP 2,RP 3, and RP 5 (and, in this example, is assigned an IP address of239.2.1.12). However, it may take time for those “matching” downlink IPmulticast groups to all be formed.

For example, when UE A first accesses the cell 108 and a downlink IPmulticast group including RP 1, RP 2, and RP 4 has not yet been created,downlink IQ data can be sent to the RPs in the simulcast zone for UE A(that is, to RP 1, RP 2, and RP 4) using the “all RP” downlink IPmulticast group (which in this example is assigned an IP address of239.2.1.1). In this case, as shown in FIG. 3 , packets includingdownlink IQ data intended for the RPs in the simulcast zone for UE A aresent to the “all RP” downlink IP multicast group (using thecorresponding IP address of 239.2.1.1), with an application-layermulticast address of “11010” where the first bit position (correspondingto RP 1), the second bit position (corresponding to RP 2) and the fourthbit position (corresponding to RP 4) are set and the third bit position(corresponding to RP 3) and the fifth bit position (corresponding to RP5) are cleared. In this example, only five bit positions are shown forease of illustration though the application-layer multicast addresstypically would use a larger number of bit positions (for example, 64bit positions, which corresponds to an eight-byte address).

After the downlink IP multicast group including RP 1, RP 2, and RP 4 iscreated, packets including downlink IQ data intended for the RPs in thesimulcast zone for UE A are sent to that downlink IP multicast group(using the corresponding IP address of 239.2.1.10), with the sameapplication-layer multicast address of “11010.”

Also, in this example, packets including downlink IQ data for commonmessages (such as SIBs) are sent to the “all RP” downlink IP multicastgroup (using the corresponding IP address of 239.2.1.1), with anapplication-layer multicast address of “11111” (because the data isintended for all RPs).

FIG. 4 is a diagram illustrating one exemplary embodiment of a protocolstack 400 suitable for communicating IQ data between each controller 104and the associated radio points 106 over the front-haul 118. Thecontroller 104 and each associated radio point 106 implements arespective signal processing peer entity 402 and 404, respectively, thatimplements the protocol stack 400.

As shown in FIG. 4 , the highest layer of the protocol stack 400comprises the application layer protocol 406 that is used forcommunicating IQ data over the fronthaul 118 between the controller 104and each radio point 106. As noted above, the IQ data communicated overthe fronthaul 118 is used in the digital signal processing that isperformed in order to implement the wireless interface for the cell 108.

In this example, the application layer protocol 406 is also referred tohere as the “Switched IQ DSP Application Protocol” or “SwIQ-DAP” layer406. Because many different types of IQ data can be communicated betweenthe controller 104 and each radio point 106 over the fronthaul 118, theIQ data is communicated using Type-Length-Value (TLV) elements 500,which are illustrated in FIG. 5 . Each TLV element 500 comprises a typefield 502 that identifies what type and format of IQ data is containedin that element 500, a length field 504 that identifies how long thatelement 500 is, and a value field 506 that contains the data or payloadfor that element 500. The type field 502 and length field 504 have afixed length, whereas the length of the value field 506 can vary.

In this example, as shown in FIG. 5 , one or more TLV elements 500 arecombined together into a single SwIQ-DAP protocol data unit (PDU) 508.Each such SwIQ-DAP PDU 508 includes a header 510 and a payload 512comprising one or more TLV elements 500 (the number of which depends onthe maximum transmission unit (MTU) size specified for the SwIQ-DAP PDUs508). In this example, the SwIQ-DAP header 510 comprises a sourceidentifier field 514 that is used to identify the sender of the PDU 508.In one embodiment where there is only one controller 104 that serveseach cell 108, the source identifier field 514 is only used to foruplink data in order to identify which RP 106 has sent a SwIQ-DAP PDU508 to that one controller 104 (since multiple RPs 106 can send suchPDUs 508 to the controller 104) but is left undefined for downlinkSwIQ-DAP PDUs 508 that are sent from the controller 104 (since there isonly one controller 104 that serves the cell 108). In another embodimentwhere multiple controllers 104 serve each cell 108, the sourceidentifier field 514 is used both to identify which RP 106 has sent eachuplink SwIQ-DAP PDU 508 to the controllers 104 and to identify whichcontroller 104 has sent each downlink SwIQ-DAP PDU 508 to one or moreRPs 106.

In this example, the SwIQ-DAP header 510 also comprises a version numberfield 516 that identifies the version number for the SwIQ-DAP, a numberof TLVs field 518 that specifies the number of TLV elements 500 that areincluded in that PDU 508, a sequence number 520 that specifies atransmission sequence number for that PDU 508, a length field 522 thatspecifies the length of that PDU 508, and a timestamp field 524 thatcontains a time stamp specifying when that PDU 508 was sent. In thisexample, the SwIQ-DAP header 510 also comprises an application-layermulticast address field 526 that can be used to specify a multicastgroup of radio points 106 at the application layer level. This can bedone as described above in connection with FIG. 3 , where each bitposition of the application-layer multicast address field 526 isassociated with a respective radio point 106, where that bit position isset if the associated downlink IQ data is intended for that radio point106 and where that bit positioned is cleared if the associated downlinkIQ data is not intended for that radio point 106.

As shown in FIG. 4 , the next layers of the protocol stack 400 comprisesthe User Datagram Protocol (UDP) layer 408 and the Internet Protocol(IP) layer 410 via which UDP datagrams encapsulated in IP packets arecommunicated between the controller 104 and the radio points 106. Asshown in FIG. 5 , each SwIQ-DAP PDU 508 is transmitted as a UDP datagramthat is encapsulated in the payload 528 of an IP packet 530. Each IPpacket 530 also includes a header 532 including the standard IP and UDPheader information.

As noted above, the fronthaul 118 is implemented using a standardswitched Ethernet network 120. Therefore, the lowest layer (data linklayer) of the protocol stack 400 is an Ethernet layer 412 (shown in FIG.4 ) via which Ethernet frames 534 (shown in FIG. 5 ) are communicatedover the Ethernet network 120 between the controller 104 and the radiopoints 106. As shown in FIG. 5 , each Ethernet frame 534 includes astandard Ethernet header 536 and a payload 538. One or more IP packets530 are encapsulated in the payload 538 of each Ethernet frame 534.

The protocol stack 400 is configured so that IQ fronthaul data can becommunicated over the fronthaul 118 of a C-RAN 100 using a standardswitched Ethernet network 120 (instead of conventional synchronous CPRIpoint-to-point links). Various standard features provided by the UDP,IP, and Ethernet layers 408, 410, and 412 (for example, port numbers, IPmulticast groups, VLANs, and packet tagging) can be used to help satisfythe requirements for the fronthaul 118 while additional featuresimplemented in the application layer 402 are used where needed.

As noted above, different splits in the wireless-interface processingbetween the controller 104 and the radio points 106 can be used for eachof the physical channels of the wireless interface. FIG. 6 illustratesone example of the different splits in the wireless-interface processingbetween the controller 104 and the radio points 106 that can be used forthe various downlink channels provided via an LTE wireless interface. Inthe example shown in FIG. 6 , the serving controller 104 performs theLayer-3 (L3) and Layer-2 (L2) processing for the LTE wireless interface,whereas different splits in the Layer-1 (physical layer) processing forthe wireless interface are used for the different LTE downlink channels.

In the example shown in FIG. 6 , downlink Layer-1 signal generation andmodulation for the Primary Synchronization Signals (PSS) and SecondarySynchronization Signals (SSS) are performed entirely in the radio points106. Likewise, in the example shown in FIG. 6 , downlink Layer-1 signalgeneration and modulation for the Cell-Specific Reference Signals(CS-RSs) and Channel State Information Reference Signals (CSI-RSs) areperformed entirely in the radio points 106. By generating these signalsin each radio point 106, in the event that downlink IQ data for one ormore of the downlink channels is corrupted or missing, the radio point106 can continue to send these synchronization and reference signals. Bydoing this, the UEs 112 can continue to remain synchronized to the cell108 and provide channel quality information (CQI). Also, generatingthese signals in each radio point 106 reduces the amount of fronthaulbandwidth that is required (since no baseband data needs to befront-hauled for these signals).

In the example shown in FIG. 6 , for the Physical Broadcast Channel(PBCH), the downlink Layer-1 signal processing for the LTE wirelessinterface up to, and including, the scrambling function are performed inthe controller 104, whereas the remaining functions (including themodulation and precoding functions) are performed in the radio points106.

In the example shown in FIG. 6 , for the Physical Control FormatIndicator Channel (PCFICH) and the Physical Downlink Control Channel(PDCCH), the downlink Layer-1 signal processing for the LTE wirelessinterface up to, and including, the scrambling function are performed inthe controller 104, whereas the remaining functions (including themodulation and precoding functions) are performed in the radio points106. Also, for the PCFICH and PDCCH, a portion of RE mapping function(determination of where the various bits generated for these channelsshould be placed in the resource grid) is also performed in thecontroller 104, where the rest of the RE mapping function is performedin each radio point 106.

In the example shown in FIG. 6 , for the Physical Control Hybrid-ARQIndicator Channel (PHICH), the downlink Layer-1 signal processing forthe LTE wireless interface up to, and including, the scrambling andmodulation functions are performed in the controller 104, whereas theremaining functions (including the precoding function) are performed inthe radio points 106. Also, for the PHICH, a portion of RE mappingfunction (determination of where the various bits generated for thischannel should be placed in the resource grid) is also performed in thecontroller 104, where the rest of the RE mapping function is performedin each radio point 106. Moreover, the frequency-domain IQ data that isproduced in the controller 104 for the PHICH is quantized before beingtransmitted over the switched Ethernet network 120 in order to compressthe baseband data and reduce the amount of fronthaul bandwidth that isused to transmit the baseband data. At each radio point 106, thisquantized data is dequantized before precoding is performed. In thisexample, a lossless quantization scheme is used (for example, one of thelossless quantization schemes described in United States PatentApplication No. US 2014/0219162).

In the example shown in FIG. 6 , for the Physical Downlink SharedChannel (PDSCH), Machine Type Communication (MTC) Physical DownlinkControl Channel (MPDCCH), and MTC Physical Downlink Shared Channel(MPDSCH), the downlink Layer-1 signal processing for the LTE wirelessinterface up to, and including, the scrambling function for the data tobe transmitted and the generation of the associated demodulationreference signal (DMRSs) are performed in the controller 104, whereasthe remaining functions (including modulation, layer mapping, andprecoding functions) are performed in the radio points 106.

As shown in FIG. 6 , the resulting symbols generated for each channel(along with the synchronization and reference signals) are inserted intothe LTE resource grid by the resource element (RE) mapping function thatis implemented in each RP 106. The resulting symbols generated by the REmapping function are then converted to time domain IQ data and a cycleprefix (CP) is appended by an Inverse Fast Fourier Transform (iFFT) andCP addition function that is implemented in each RP 106. The resultingtime-domain IQ data is then used to generate the corresponding downlinkanalog RF signals by a Digital-to-RF conversion function that isimplemented in each RP 106. In this example, the Digital-to-RFconversion function is implemented in the RF module 182 in each RP 106,whereas the other functions described here in connection with FIG. 6 asbeing implemented in each RP 106 are implemented using the programmabledevices 186 in each RP 106.

Other splits in the wireless-interface processing between the controller104 and the radio points 106 can be used. Another example is shown inFIG. 7 .

FIG. 7 illustrates one example of the different splits in thewireless-interface processing between the controller 104 and the radiopoints 106 that can be used for the downlink channels of a FifthGeneration (5G)-New Radio (NR) wireless interface. In the example shownin FIG. 7 , the serving controller 104 performs the L3 and L2 processingfor the wireless interface, whereas different splits in the L1processing for the wireless interface are used for the different 5G-NRdownlink channels.

In the example shown in FIG. 7 , downlink Layer-1 signal generation andmodulation for the PSS and SSS are performed entirely in the radiopoints 106. Likewise, in the example shown in FIG. 7 , downlink Layer-1signal generation and modulation for the Phase Tracking ReferenceSignals (PTRSs) and CSI-RSs are performed entirely in the radio points106. This is done for the same general reasons described above inconnection with FIG. 6 .

In the example shown in FIG. 7 , for the PBCH, the downlink Layer-1signal processing for the 5G-NR wireless interface up to, and including,the scrambling function for the data to be transmitted and thegeneration of the associated DMRSs are performed in the controller 104,whereas the remaining functions (including the modulation and precodingfunctions) are performed in the radio points 106.

In the example shown in FIG. 7 , for the PDCCH, the downlink Layer-1signal processing for the 5G-NR wireless interface up to, and including,the scrambling function for the data to be transmitted and thegeneration of the associated DMRSs are performed in the controller 104,whereas the remaining functions (including the modulation and precodingfunctions) are performed in the radio points 106. Also, for the PDCCH, aportion of RE mapping function (determination of where the various bitsgenerated for this channel should be placed in the resource grid) isalso performed in the controller 104, where the rest of the RE mappingfunction is performed in each radio point 106.

In the example shown in FIG. 7 , for the PDSCH, the downlink Layer-1signal processing for the 5G-NR wireless interface up to, and including,the scrambling function for the data to be transmitted and thegeneration of the associated DMRSs are performed in the controller 104,whereas the remaining functions (including modulation, layer mapping,and precoding functions) are performed in the radio points 106.

As shown in FIG. 7 , the resulting symbols generated for each channel(along with the synchronization and reference signals) are inserted intothe 5G-NR resource grid by the RE mapping function that is implementedin each RP 106. The resulting symbols generated by the RE mappingfunction are then converted to time domain IQ data and a CP is appendedby an iFFT and CP addition function that is implemented in each RP 106.The resulting time-domain IQ data is then used to generate thecorresponding downlink analog RF signals by a digital-to-RF conversionfunction that is implemented in each RP 106. Also, any (optional) analogbeamforming for any of the channels is also implemented in each RP 106.In this example, the digital-to-RF conversion function and any analogbeamforming is implemented in the RF module 182 in each RP 106, whereasthe other functions described here in connection with FIG. 7 as beingimplemented in each RP 106 are implemented using the programmabledevices 186 in each RP 106.

FIG. 8 illustrates another example of a split in the wireless-interfaceprocessing between the controller 104 and the radio points 106 that canbe used with the PDSCH. This approach is used when both licensed andunlicensed radio frequency spectrum is used to serve a UE 112 in thedownlink (for example, by implementing the Licensed Assisted Access(LAA) wireless protocol).

For the licensed RF spectrum, the downlink Layer-1 signal processing forthe PDSCH up to, and including, the scrambling function for the data tobe transmitted and the generation of the associated DMRSs are performedin the controller 104, whereas the remaining functions (includingmodulation, layer mapping, and precoding functions) are performed in theradio points 106. However, a different split is used for the unlicensedRF spectrum. This is done because each radio point 106 must separatelyuse the listen before talk (LBT) protocol in order to gain access to theunlicensed RF spectrum. To support the use of the LBT protocol in eachradio point 106, for the unlicensed RF spectrum, the downlink Layer-1signal processing for the PDSCH up to, and including, the cyclicredundancy code (CRC) generation function and the turbo encoding andrate matching function for the data to be transmitted are performed inthe controller 104, whereas the remaining functions (including thefunctions of scrambling the data to be transmitted, generation of theassociated DMRSs, modulation, layer mapping, and precoding) areperformed in each radio point 106 after the radio point 106 gains accessto the unlicensed RF spectrum via the LBT protocol. That is, when PDSCHdata is to be transmitted from a radio point 106 using unlicensed RFspectrum, the L2 processing and some of the L1 processing for that datais performed in the controller 104 and the resulting baseband data issent over the fronthaul 118 to the appropriate radio point 106. Theradio point 106 performs the LBT protocol in order to gain access to theunlicensed RF spectrum and, once it is successful, the radio point 106scrambles the baseband data based on the new transmit (Tx) sub-framenumber and performs the rest of the L1 processing as described above.

As noted above, in the example described above, IQ data is communicatedbetween the controller 104 and each radio point 106 over the fronthaul118 using TLV elements 500.

For example, where the split in the wireless-interface processingbetween the controller 104 and the radio points 106 for the PDSCH is asdescribed above in FIG. 6, 7 , or 8, the controller 104 performsscrambling, CRC addition, code block (CB) segmentation, CB and CRCaddition (if applicable), and rate matching. The encoded bits for theresulting codewords (CWs) are communicated from the controller 104 tothe appropriate radio points 106 on a per-UE, per-codeword, andper-subframe (a subframe is also known as a “transmission-time-interval”or “TTI”) basis using one type of TLV element 500. One example of such aTLV element is shown in FIG. 9 . This type of TLV element can also beused when scrambling is performed in the radio points 106 instead of inthe controller 104.

FIG. 9 illustrates one exemplary embodiment of a TLV element 900 forcommunicating downlink IQ data over the fronthaul 118 in the C-RAN 100described here. This TLV element 900 is also referred to here as the“DL-PDSCH-1CW-FEC_BITS-D” TLV type. This DL-PDSCH-1CW-FEC_BITS-D TLVtype is used by the SwIQ-DAP layer 406 for communicating each code word(CW) in the LTE wireless protocol in the PDSCH. In this example, the IQdata (that is, Layer-1 data) is communicated from the controller 104 tothe radio points 106 on a per-UE, per-codeword, and per-subframe basis,where the SwIQ-DAP layer 406 in the controller signal processing peer402 fragments each CW for each UE, codeword, and subframe into segmentsas needed prior to transmission over the fronthaul 118 and the SwIQ-DAPlayer 406 in the radio point signal processing peer 404 re-assembles thereceived segments. This DL-PDSCH-1CW-FEC_BITS-D TLV type can be used forboth MIMO and Transmit Diversity transmission modes. In this example,for each UE 112 wirelessly transmitted to using the PDSCH during eachTTI, the IQ data for that UE 112 can be communicated from the controller104 to the radio points 106 in that UE's simulcast zone using multipleTLV elements 900 that are combined together into a singleapplication-layer PDU, where each resulting application-layer PDU isassociated with a single UE. In this example, if the Ethernet MaximumTransmission Unit (MTU) used in the switched Ethernet network 120 islarge enough, a single Ethernet packet may carry data for two layers.However, in this example, a single Ethernet packet is used to carry datafor two slots if the resulting Ethernet packet has a size that is lessthan 256 bytes.

Each DL-PDSCH-1CW-FEC_BITS-D TLV element 900 comprises a type field 902and a length field 904, which comprise the type field 502 and lengthfield 504 as described above in connection with FIG. 5 . Morespecifically, the value stored in the type field 902 is a valueindicating that the element 900 is a DL-PDSCH-1CW-FEC_BITS-D TLVelement, and the value stored in the length field 904 comprises thelength of the particular element 900.

Each DL-PDSCH-1CW-FEC_BITS-D TLV element 900 also comprises a valueportion 905 comprising several fields that make up the “value” part ofthe TLV element 900.

The value portion 905 of the DL-PDSCH-1CW-FEC_BITS-D TLV element 900comprises a PDU Index/Sequence Number field 906 that is used to store arunning number that is the same for all fragments of a given code word.The running number stored in the PDU Index/Sequence Number field 906 isreset for each TTI and is unique for each carrier served by a controller104. If carrier aggregation is used, this running number is unique foreach carrier that is aggregated (even if the various carriers are servedby different controllers 104).

The value portion 905 of the DL-PDSCH-1CW-FEC_BITS-D TLV element 900also comprises a Radio Network Temporary Identifier (RNTI) field 908that stores the RNTI for the associated CW. The value portion 905 of theDL-PDSCH-1CW-FEC_BITS-D TLV element 900 also comprises a UE Index field910 that is used to store an index value assigned to the UE for theassociated CW. This field 910 can be used by the RP 106 in identifyingDL-PDSCH-1CW-FEC_BITS-D TLV elements 900 that are associated with theRNTI. The value portion 905 of the DL-PDSCH-1CW-FEC_BITS-D TLV element900 also comprises a carrier number field 912 that is used to store anindex value assigned to the carrier for the associated CW. This indexvalue is useful when carrier aggregation is used and there is a need todistinguish between the various carriers used to serve a given UE.

In this example, the value portion 905 of the DL-PDSCH-1CW-FEC_BITS-DTLV element 900 also comprises padding 914 and a sub-TLV portion 915.The padding 914 is used so that the sub-TLV portion 915 of each element900 can be aligned to a preferred boundary. The padding 914 is optional;in other embodiments, padding 914 is not used. The sub-TLV portion 915of each element 900 comprises one or more sub-TLV elements. In thisexample, there are two different types of sub-TLV elements. The firsttype of sub-TLV element 916 is used to communicate the configuration forthe associated CW as well as the first segment of encoded bits for theCW. This first type of sub-TLV element 916 is also referred to here asthe “PDSCH-CONFIG-and-FEC-BITS” sub-TLV element 916. The second type ofsub-TLV element 918 is used to communicate subsequent segments ofencoded bits for the CW. This second type of sub-TLV element 918 is alsoreferred to here as the “PDSCH-PADDING-and-FEC-BITS” sub-TLV element918.

As shown in FIG. 10 , the PDSCH-CONFIG-and-FEC-BITS sub-TLV element 916comprises a sub-TLV type field 922 and a sub-TLV length field 924. Thesub-TLV type field 922 stores a value that indicates what type ofsub-TLV element that element is, which in this case is a valueindicating that the sub-TLV element is a PDSCH-CONFIG-and-FEC-BITSsub-TLV element 916. The sub-TLV length field 924 is used to store thelength of that element 916.

The PDSCH-CONFIG-and-FEC-BITS sub-TLV element 916 also comprises a valueportion 926. The value portion 926 of the PDSCH-CONFIG-and-FEC-BITSsub-TLV element 916 comprises a downlink channel configuration typefield 928 that is used to store a value identifying the configuration ofthe downlink channel. In this example, the value can indicate whetherthe downlink channel is configured to use a particular unicast downlinkchannel transmission mode (for example, transmission mode 4 usingtransmit diversity, transmission mode 4 using closed loop spatialmultiplexing, or transmission mode 9) or is configured as a multicastdownlink channel (that, as a Physical Multicast Channel (PMCH)).

The value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916 also comprises a UE release field 930 that is used to store a valueindicating the UE release (which is used for mapping CSI-RSs andDM-RSs), a modulation order field 932 that is used to store a valueindicating the modulation order or scheme to use for the downlinkchannel, and a PA value field 934 that is used store a value indicatingthe power of the PDSCH RE in non CS-RS symbols, which can be used tocalculate gain values for the PDSCH in the RP 106.

The value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916 also comprises a resource allocation type (RAT) field 936 that isused store a value indicating which RAT should be used, a resource block(RB) coding field 938 that is used store a value indicating the RBcoding used by the baseband modules in the controller 104 to get the RBallocation for the UE 112, and a scrambling initialization (C-Init)field 940 that is used to store the C-Init value used for scrambling(which is used if scrambling is performed in the radio point 106).

The value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916 also comprises a total transport block (TB) length field 942 that isused to store the length of the corresponding transport block afterscrambling, a scrambling identifier (SCID) field 944 that is used storethe scrambling ID used for UE-specific reference symbols, a DMRSidentifier field 946 that is used store a DMRS identifier (which in thisexample is the same as physical cell identifier unless a differentidentifier is specified by the higher layers). The values stored in theSCID field 944 and the DMRS identifier field 946 are only used when thedownlink channel configuration type field 928 indicates that thedownlink channel is configured to use transmission mode 9 (ortransmission mode 10 if that mode is also supported).

The value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916 also comprises a Multicast Broadcast Single Frequency Network(MBSFN) identifier field 948 that is used to store a MBSFN identifierfor the associated UE 112, which is only used when the downlink channelconfiguration type field 928 indicates that the downlink channel isconfigured as a multicast downlink channel (PMCH).

The value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916 also comprises a number of sub-bands field 950 that is used storethe number of sub-bands that the PDSCH is divided into, a sub-bandinformation field 952 that is used store, for each sub-band, an indexvalue for the precoding matrix or the code book used for precoding ofthat sub-band, a number of resource blocks (RBs) field 954 that is usedto store the number of RBs allocated to the associated UE 112, and anumber layers field 956 that is used to store the number of layers onwhich the downlink channel will be transmitted.

The value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916 also comprises a bits field 958 that comprises the actual “payload”for the sub-TLV element 916 and is used to store the bits for thesegment of the CW communicated in that sub-TLV element 916. In thoseembodiments where the scrambling is performed in the controller 104,these bits are scrambled and are forwarded to the modulation function inthe RP 106. In those embodiments where the scrambling is performed inthe radio point 106, these bits are not scrambled and are forwarded tothe scrambling function in the RP 106. The exact size of the bits field958 varies and depends on factors such as the transport block size andthe resource allocation.

As shown in FIG. 11 , each PDSCH-PADDING-and-FEC-BITS sub-TLV elements918 comprises a sub-TLV type field 922 and a sub-TLV length field 924,which are the same as in the PDSCH-CONFIG-and-FEC-BITS sub-TLV element916.

Each PDSCH-PADDING-and-FEC-BITS sub-TLV element 918 also comprises avalue portion 960 that includes padding 962 and a bits field 958. Inthis example, the padding 962 is used so that the bits field 958 will belocated in the value portion 960 of the PDSCH-PADDING-and-FEC-BITSsub-TLV element 918 at the same offset as the bits field 958 is locatedin the value portion 926 of the PDSCH-CONFIG-and-FEC-BITS sub-TLVelement 916. The bits field 958 of the PDSCH-PADDING-and-FEC-BITSsub-TLV element 918 is used in the same way as the bits field 958 of thePDSCH-CONFIG-and-FEC-BITS sub-TLV element 916.

The TLV elements portrayed in FIGS. 9, 10 and 11 can also be used fortransmitting codewords (CVV) of the PDSCH of the 5G-NR wireless protocolusing the previously described techniques on a per-UE, per-CW andper-slot basis, where it is understood that the notion of subframe inLTE corresponds to the notion of slot in 5G-NR.

The methods and techniques described here may be implemented in digitalelectronic circuitry, or with a programmable processor (for example, aspecial-purpose processor or a general-purpose processor such as acomputer) firmware, software, or in combinations of them. Apparatusembodying these techniques may include appropriate input and outputdevices, a programmable processor, and a storage medium tangiblyembodying program instructions for execution by the programmableprocessor. A process embodying these techniques may be performed by aprogrammable processor executing a program of instructions to performdesired functions by operating on input data and generating appropriateoutput. The techniques may advantageously be implemented in one or moreprograms that are executable on a programmable system including at leastone programmable processor coupled to receive data and instructionsfrom, and to transmit data and instructions to, a data storage system,at least one input device, and at least one output device. Generally, aprocessor will receive instructions and data from a read-only memoryand/or a random-access memory. Storage devices suitable for tangiblyembodying computer program instructions and data include all forms ofnon-volatile memory, including by way of example semiconductor memorydevices, such as EPROM, EEPROM, and flash memory devices; magnetic diskssuch as internal hard disks and removable disks; magneto-optical disks;and DVD disks. Any of the foregoing may be supplemented by, orincorporated in, specially-designed application-specific integratedcircuits (ASICs).

A number of embodiments of the invention defined by the following claimshave been described. Nevertheless, it will be understood that variousmodifications to the described embodiments may be made without departingfrom the spirit and scope of the claimed invention. Accordingly, otherembodiments are within the scope of the following claims.

Example Embodiments

Example 1 includes a system to provide wireless service comprising: atleast one controller; and a plurality of radio points; wherein each ofthe radio points is associated with at least one antenna and remotelylocated from the controller, wherein the plurality of radio points iscommunicatively coupled to the controller; wherein the controller andthe plurality of radio points are configured to implement at least onebase station in order to provide wireless service via a wirelessinterface to a plurality of user equipment (UEs) using at least onecell; wherein the controller is communicatively coupled to a corenetwork of a wireless service provider; wherein the system is configuredso that physical layer processing for the wireless interface is split sothat some of the physical layer processing is performed in thecontroller and some of the physical layer processing is performed in theradio points; and wherein the system is configured so that scrambling offirst downlink data to be communicated to a UE over the wirelessinterface is performed in the controller and so that scrambling ofsecond downlink data to be communicated to said UE over the wirelessinterface is performed in at least one of the radio points.

Example 2 includes the system of Example 1, wherein the system isconfigured so that the first downlink data to be communicated to said UEover the wireless interface is communicated to said UE over the wirelessinterface using licensed radio frequency spectrum.

Example 3 includes the system of any of Examples 1-2, wherein the systemis configured so that the second downlink data to be communicated tosaid UE over the wireless interface is communicated to said UE over thewireless interface using unlicensed radio frequency spectrum.

Example 4 includes the system of Example 3, wherein the system isconfigured so that the second downlink data is front-hauled from thecontroller to said one of the radio points in an unscrambled form,wherein the scrambling of the second downlink data to be communicated tosaid UE over the wireless interface is performed in said one of theradio points after said one of the radio points gains access to theunlicensed radio frequency spectrum.

Example 5 includes the system of Example 4, wherein the system isconfigured so that said one of the radio points gains access to theunlicensed radio frequency spectrum using a Listen Before Talk (LBT)protocol.

Example 6 includes the system of any of Examples 3-5, wherein the systemis configured so that the second downlink data to be communicated tosaid UE over the wireless interface is communicated to said UE over thewireless interface using unlicensed radio frequency spectrum andLong-Term Evolution (LTE) Licensed Assisted Access (LAA).

Example 7 includes the system of any of Examples 1-6, wherein the systemis configured so that the first and second data is front-hauled from thecontroller to said one of the radio points in a common format, whereinthe common format supports communicating information needed forperforming the scrambling of the second downlink data in said one of theradio points.

Example 8 includes the system of any of Examples 1-7, wherein the systemis configured so that the common format comprises one or moretype-length-value (TLV) elements.

Example 9 includes the system of Example 8, wherein the system isconfigured so that each TLV element can comprise one or more sub-TLVelements, one sub-TLV element comprising configuration information andbits for the data to be communicated over the wireless interface, theconfiguration information including the information need for performingthe scrambling of the second downlink data in said one of the radiopoints.

Example 10 includes the system of any of Examples 1-9, wherein thesystem is configured to fronthaul data between the controller and theradio points using a switched Ethernet network.

Example 11 includes the system of Example 10, wherein the system isconfigured to fronthaul data between the controller and the radio pointsusing a protocol stack comprising an application layer, an InternetProtocol (IP) layer, and an Ethernet layer; wherein the applicationlayer is configured in order to enable fronthaul data to be associatedwith an application-layer multicast address; wherein the IP layer isconfigured in order to enable fronthaul data to be associated with an IPmulticast address; and wherein the application layer is configured sothat the application-layer multicast address indicates which radiopoints the associated fronthaul data is intended for.

Example 12 includes the system of Example 11, wherein the applicationlayer is configured so that the application-layer multicast addressindicates which radio points the associated fronthaul data is intendedfor if the respective IP multicast address associated with thatfronthaul data includes radio points other than the radio points thatfronthaul data is intended for.

Example 13 includes the system of any of Examples 11-12, wherein thesystem is configured to dynamically create IP multicast groups based onrespective subsets of the radio points used to communicate data to theUEs; and wherein the system is configured so that the IP multicastgroups include one IP multicast group that includes all of the radiopoints.

Example 14 includes a system to provide wireless service comprising: atleast one controller; and a plurality of radio points; wherein each ofthe radio points is associated with at least one antenna and remotelylocated from the controller, wherein the plurality of radio points iscommunicatively coupled to the controller; wherein the controller andthe plurality of radio points are configured to implement at least onebase station in order to provide wireless service via a Long-TermEvolution (LTE) wireless interface to a plurality of user equipment(UEs) using at least one cell; wherein the controller is communicativelycoupled to a core network of a wireless service provider; wherein thesystem is configured so that physical layer processing for the wirelessinterface is split so that some of the physical layer processing isperformed in the controller and some of the physical layer processing isperformed in the radio points; and wherein the system is configured sothat: signal generation and modulation for Primary SynchronizationSignals (PSS) and Secondary Synchronization Signals (SSS) are performedentirely in the radio points; signal generation and modulation forCell-Specific Reference Signals (CS-RSs) and Channel State InformationReference Signals (CSI-RSs) are performed entirely in the radio points;for a Physical Downlink Control Channel (PDCCH), downlink Layer-1 signalprocessing for the LTE wireless interface up to, and including, ascrambling function is performed in the controller, wherein a portion ofa resource element (RE) mapping function for the PDCCH is also performedin the controller, wherein the downlink Layer-1 signal processing forthe PDCCH not performed in the controller is performed in the radiopoints; and for a Physical Downlink Shared Channel (PDSCH), downlinkLayer-1 signal processing for the LTE wireless interface up to, andincluding, a scrambling function for data to be transmitted andgeneration of associated demodulation reference signals (DMRSs) areperformed in the controller, wherein the downlink Layer-1 signalprocessing for the PDSCH not performed in the controller is performed inthe radio points.

Example 15 includes the system of Example 14, wherein the system isfurther configured so that: for a Physical Broadcast Channel (PBCH),downlink Layer-1 signal processing for the LTE wireless interface up to,and including, a scrambling function is performed in the controller,wherein the downlink Layer-1 signal processing for the PBCH notperformed in the controller is performed in the radio points.

Example 16 includes the system of any of Examples 14-15, wherein thesystem is further configured so that: for a Physical Control FormatIndicator Channel (PCFICH), downlink Layer-1 signal processing for theLTE wireless interface up to, and including, a scrambling function isperformed in the controller, wherein a portion of a resource element(RE) mapping function for the PCFICH is also performed in thecontroller, wherein the downlink Layer-1 signal processing for thePCFICH not performed in the controller is performed in the radio points.

Example 17 includes the system of Example 16, wherein the system isconfigured so that the data produced in the controller for the PHICH isquantized to produce quantized data, wherein the quantized data iscommunicated to the radio points, wherein the radio points dequantizethe quantized data before the downlink Layer-1 signal processing for thePCFICH not performed in the controller.

Example 18 includes the system of any of Examples 14-17, wherein thesystem is further configured so that: for a Machine Type Communication(MTC) Physical Downlink Control Channel (MPDCCH), downlink Layer-1signal processing for the LTE wireless interface up to, and including, ascrambling function for data to be transmitted and generation ofassociated DMRSs are performed in the controller, wherein the downlinkLayer-1 signal processing for the MPDCCH not performed in the controlleris performed in the radio points; and for a MTC Physical Downlink SharedChannel (MPDSCH), downlink Layer-1 signal processing for the LTEwireless interface up to, and including, a scrambling function for datato be transmitted and generation of associated DMRSs are performed inthe controller, wherein the downlink Layer-1 signal processing for theMPDSCH not performed in the controller is performed in the radio points.

Example 19 includes the system of any of Examples 14-18, wherein thesystem is configured so that data is front-hauled from the controller tosaid one of the radio points using type-length-value (TLV) elements inwhich different types of data can be communicated.

Example 20 includes the system of any of Examples 14-19, wherein thesystem is configured to fronthaul data between the controller and theradio points using a switched Ethernet network.

Example 21 includes the system of any of Examples 14-20, wherein thesystem is configured to fronthaul data between the controller and theradio points using a protocol stack comprising an application layer, anInternet Protocol (IP) layer, and an Ethernet layer; wherein theapplication layer is configured in order to enable fronthaul data to beassociated with an application-layer multicast address; wherein the IPlayer is configured in order to enable fronthaul data to be associatedwith an IP multicast address; and wherein the application layer isconfigured so that the application-layer multicast address indicateswhich radio points the associated fronthaul data is intended for.

Example 22 includes the system of any of Examples 14-21, wherein theapplication layer is configured so that the application-layer multicastaddress indicates which radio points the associated fronthaul data isintended for if the respective IP multicast address associated with thatfronthaul data includes radio points other than the radio points thatfronthaul data is intended for.

Example 23 includes the system of any of Examples 21-22, wherein thesystem is configured to dynamically create IP multicast groups based onrespective subsets of the radio points used to communicate data to theUEs; and wherein the system is configured so that the IP multicastgroups include one IP multicast group that includes all of the radiopoints.

Example 24 includes the system of any of Examples 14-23, wherein aportion of a RE mapping function for at least one physical downlinkchannel is performed in the radio points.

Example 25 includes the system of any of Examples 14-24, wherein thesystem is configured to fronthaul Layer-1 data between the controllerand at least some of the radio points on a per-subframe basis.

Example 26 includes the system of any of Examples 14-25, wherein thesystem is configured to fronthaul Layer-1 data between the controllerand at least some of the radio points on a per-codeword basis.

Example 27 includes the system of any of Examples 14-26, wherein thesystem is configured, for each UE wirelessly transmitted to using thePDSCH during each subframe, to fronthaul Layer-1 data for that UE fromthe controller to at least some of the radio points in a singleapplication-layer protocol data unit.

Example 28 includes system to provide wireless service comprising: atleast one controller; and a plurality of radio points; wherein each ofthe radio points is associated with at least one antenna and remotelylocated from the controller, wherein the plurality of radio points iscommunicatively coupled to the controller; wherein the controller andthe plurality of radio points are configured to implement at least onebase station in order to provide wireless service via a Fifth GenerationNew Radio (5G-NR) wireless interface to a plurality of user equipment(UEs) using at least one cell; wherein the controller is communicativelycoupled to a core network of a wireless service provider; wherein thesystem is configured so that physical layer processing for the wirelessinterface is split so that some of the physical layer processing isperformed in the controller and some of the physical layer processing isperformed in the radio points; and wherein the system is configured sothat: signal generation and modulation for Primary SynchronizationSignals (PSS) and Secondary Synchronization Signals (SSS) are performedentirely in the radio points; signal generation and modulation for PhaseTracking Reference Signals (PTRSs) and Channel State InformationReference Signals (CSI-RSs) are performed entirely in the radio points;for a Physical Downlink Control Channel (PDCCH), downlink Layer-1 signalprocessing for the 5G-NR wireless interface up to, and including, ascrambling function for data to be transmitted and generation ofassociated demodulation reference signals (DMRSs) are performed in thecontroller, wherein a portion of a resource element (RE) mappingfunction for the PDCCH is also performed in the controller, wherein thedownlink Layer-1 signal processing for the PDCCH not performed in thecontroller is performed in the radio points; and for a Physical DownlinkShared Channel (PDSCH), downlink Layer-1 signal processing for the 5G-NRwireless interface up to, and including, a scrambling function for datato be transmitted and generation of associated DMRSs are performed inthe controller, wherein the downlink Layer-1 signal processing for thePDSCH not performed in the controller is performed in the radio points.

Example 29 includes the system of Example 28, wherein the system isfurther configured so that: for a Physical Broadcast Channel (PBCH),downlink Layer-1 signal processing for the 5G-NR wireless interface upto, and including, a scrambling function for data to be transmitted andgeneration of associated DMRSs are performed in the controller, whereinthe downlink Layer-1 signal processing for the PBCH not performed in thecontroller is performed in the radio points.

Example 30 includes the system of any of Examples 28-29, wherein thesystem is configured so that data is front-hauled from the controller tosaid one of the radio points using type-length-value (TLV) elements inwhich different types of data can be communicated.

Example 31 includes the system of any of Examples 28-30, wherein thesystem is configured to fronthaul data between the controller and theradio points using a switched Ethernet network.

Example 32 includes the system of any of Examples 28-31, wherein thesystem is configured to fronthaul data between the controller and theradio points using a protocol stack comprising an application layer, anInternet Protocol (IP) layer, and an Ethernet layer; wherein theapplication layer is configured in order to enable fronthaul data to beassociated with an application-layer multicast address; wherein the IPlayer is configured in order to enable fronthaul data to be associatedwith an IP multicast address; and wherein the application layer isconfigured so that the application-layer multicast address indicateswhich radio points the associated fronthaul data is intended for.

Example 33 includes the system of Example 32, wherein the applicationlayer is configured so that the application-layer multicast addressindicates which radio points the associated fronthaul data is intendedfor if the respective IP multicast address associated with thatfronthaul data includes radio points other than the radio points thatfronthaul data is intended for.

Example 34 includes the system of any of Examples 32-33, wherein thesystem is configured to dynamically create IP multicast groups based onrespective subsets of the radio points used to communicate data to theUEs; and wherein the system is configured so that the IP multicastgroups include one IP multicast group that includes all of the radiopoints.

Example 35 includes the system of any of Examples 28-34, wherein aportion of a RE mapping function for at least one physical downlinkchannel is performed in the radio points.

Example 36 includes the system of any of Examples 28-35, wherein thesystem is configured to fronthaul Layer-1 data between the controllerand at least some of the radio points on a per-slot basis.

Example 37 includes the system of any of Examples 28-36, wherein thesystem is configured to fronthaul Layer-1 data between the controllerand at least some of the radio points on a per-codeword basis.

Example 38 includes the system of any of Examples 28-37, wherein thesystem is configured, for each UE wirelessly transmitted to using thePDSCH during each slot, to fronthaul Layer-1 data for that UE from thecontroller to at least some of the radio points in a singleapplication-layer protocol data unit.

What is claimed is:
 1. A system comprising: a plurality of basebandunits; and a shared radio point that is communicatively coupled to theplurality of baseband units using a fronthaul network and that isconfigured to serve each of the plurality of baseband units; wherein theshared radio point is configured to perform at least some Layer 1processing for implementing a respective base station for each of theplurality of baseband units; wherein the plurality of baseband unitscommunicates fronthaul data to the shared radio point using a sharedfronthaul network; wherein the system is configured to communicate atleast two different types of fronthaul data from the plurality ofbaseband units to the shared radio point using a singleapplication-layer protocol that supports at least two types of elements,wherein each of the at least two types of elements is configured for arespective one of the at least two different types of fronthaul data;and wherein the system is configured so at least some of the elementscommunicated using the application-layer protocol include one or moresub-elements, each sub-element comprising a type field, a length field,and a value portion.
 2. The system of claim 1, wherein the system isconfigured so that the application-layer protocol supportsapplication-layer fragmentation of fronthaul data into multiplesegments.
 3. The system of claim 2, wherein the system is configured sothat each segment includes a field storing a value that is used toidentify segments that are fragments of a common whole.
 4. The system ofclaim 2, wherein the system is configured to communicate messages fromthe plurality of baseband units to the shared radio point using theapplication-layer protocol, wherein each of the messages comprises afield storing a value indicating the number of elements stored in themessage.
 5. The system of claim 4, wherein the system is configured sothat the field storing the value indicating the number of elementsstored in each message is a part of an application header portion of themessage.
 6. The system of claim 1, wherein the system is configured soat least some of the elements communicated using the application-layerprotocol include a description of a range of resource blocks (RB) forwhich frequency-domain in-phase and quadrature (IQ) data is communicatedusing the application-layer protocol.
 7. The system of claim 1, whereinthe system is configured so that protocol data units for theapplication-layer protocol are encapsulated into Ethernet frames.
 8. Thesystem of claim 7, wherein the protocol data units for theapplication-layer protocol are encapsulated into Ethernet frames byfirst encapsulating the protocol data units using a second layer.
 9. Ashared radio point for use in a radio access network (RAN), the sharedradio point comprising: at least one network interface to communicativecouple the shared radio point to a plurality of baseband units using afronthaul network; at least one programmable device configured toperform at least some Layer 1 processing for implementing a respectivebase station for each of the plurality of baseband units; and aplurality of radio frequency (RF) modules to implement RF transceiverfunctions for the baseband units; wherein the shared radio point isconfigured to serve each of the plurality of baseband units; wherein theshared radio point is configured to receive fronthaul data from theplurality of baseband units; wherein the shared radio point isconfigured to receive at least two different types of fronthaul datafrom the plurality of baseband units using a single application-layerprotocol that supports at least two types of elements, wherein each ofthe at least two types of elements is configured for a respective one ofthe at least two different types of fronthaul data; and wherein theshared radio point is configured so at least some of the elementsreceived using the application-layer protocol include one or moresub-elements, each sub-element comprising a type field, a length field,and a value portion.
 10. The shared radio point of claim 9, wherein theshared radio point is configured so that the application-layer protocolsupports application-layer fragmentation of fronthaul data into multiplesegments.
 11. The shared radio point of claim 10, wherein the sharedradio point is configured so that each segment includes a respectivefield storing a value that is used to identify segments that arefragments of a common whole.
 12. The shared radio point of claim 10,wherein the shared radio point is configured to receive messages fromthe plurality of baseband units using the application-layer protocol,wherein each of the messages comprises a field storing a valueindicating the number of elements stored in the message.
 13. The sharedradio point of claim 12, wherein the shared radio point is configured sothat the field storing the value indicating the number of elementsstored in each message is a part of an application header portion of themessage.
 14. The shared radio point of claim 9, wherein the shared radiopoint is configured so at least some of the elements received using theapplication-layer protocol include a description of a range of resourceblocks (RB) for which frequency-domain in-phase and quadrature (IQ) datais received using the application-layer protocol.
 15. The shared radiopoint of claim 9, wherein the shared radio point is configured so thatprotocol data units for the application-layer protocol are encapsulatedinto Ethernet frames.
 16. The shared radio point of claim 15, whereinthe shared radio point is configured so that the protocol data units forthe application-layer protocol are encapsulated into Ethernet frames byfirst encapsulating the protocol data units using a second layer.
 17. Amethod for a shared radio point, the method comprising: communicativelycoupling the shared radio point to the plurality of baseband units usinga shared fronthaul network; performing, by the shared radio point, atleast some Layer 1 processing for implementing a respective base stationfor each of the plurality of baseband units; and receiving, by theshared radio point, fronthaul data from the plurality of baseband units;and wherein receiving, by the shared radio point, the fronthaul datafrom the plurality of baseband units comprises: receiving, by the sharedradio point, at least two different types of fronthaul data from theplurality of baseband units using a single application-layer protocolthat supports at least two types of elements, wherein each of the atleast two types of elements is configured for a respective one of the atleast two different types of fronthaul data, and wherein at least someof the elements received using the application-layer protocol includeone or more sub-elements, each sub-element comprising a type field, alength field, and a value portion.
 18. The method of claim 17, furthercomprising: fragmenting, by the application-layer protocol, fronthauldata into multiple segments.
 19. The method of claim 18, wherein eachsegment includes a respective field storing a value that is used toidentify segments that are fragments of a common whole.
 20. The methodof claim 18, wherein receiving, by the shared radio point, the fronthauldata from the plurality of baseband units comprises: receiving, by theshared radio point, messages from the plurality of baseband units usingthe application-layer protocol, wherein each of the messages comprises afield storing a value indicating the number of elements stored in themessage.
 21. The method of claim 20, wherein the field storing the valueindicating the number of elements stored in each message is a part of anapplication header portion of the message.
 22. The method of claim 17,wherein at least some of the elements received using theapplication-layer protocol include a description of a range of resourceblocks (RB) for which frequency-domain in-phase and quadrature (IQ) datais received using the application-layer protocol.
 23. The method ofclaim 17, further comprising encapsulating protocol data units for theapplication-layer protocol into Ethernet frames.
 24. The method of claim23, wherein encapsulating the protocol data units for theapplication-layer protocol into the Ethernet frames comprises firstencapsulating the protocol data units using a second layer.